diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java b/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java
index 246b95de..329afdd 100644
--- a/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java
@@ -33,7 +33,6 @@
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Date;
 import java.util.LinkedList;
 
@@ -118,9 +117,10 @@
     synchronized @Nullable LoaderTask getNextTaskOrReleaseBackgroundThread() {
         Preconditions.checkState(mBackgroundThread != null);
 
-        final LoaderTask task = mTaskList.findRunningTask();
-        if (task != null) {
-            return task;
+        for (final LoaderTask task : mTaskList) {
+            if (task.getState() == LoaderTask.STATE_LOADING) {
+                return task;
+            }
         }
 
         final Identifier identifier = mDatabase.getUnmappedDocumentsParent(mDevice.deviceId);
@@ -161,8 +161,21 @@
         mTaskList.clearCompletedTasks();
     }
 
-    synchronized void clearTask(Identifier parentIdentifier) {
-        mTaskList.clearTask(parentIdentifier);
+    /**
+     * Cancels the task for |parentIdentifier|.
+     *
+     * Task is removed from the cached list and it will create new task when |parentIdentifier|'s
+     * children are queried next.
+     */
+    void cancelTask(Identifier parentIdentifier) {
+        final LoaderTask task;
+        synchronized (this) {
+            task = mTaskList.findTask(parentIdentifier);
+        }
+        if (task != null) {
+            task.cancel();
+            mTaskList.remove(task);
+        }
     }
 
     /**
@@ -205,14 +218,6 @@
             return null;
         }
 
-        LoaderTask findRunningTask() {
-            for (int i = 0; i < size(); i++) {
-                if (get(i).getState() == LoaderTask.STATE_LOADING)
-                    return get(i);
-            }
-            return null;
-        }
-
         void clearCompletedTasks() {
             int i = 0;
             while (i < size()) {
@@ -223,17 +228,6 @@
                 }
             }
         }
-
-        void clearTask(Identifier parentIdentifier) {
-            for (int i = 0; i < size(); i++) {
-                final LoaderTask task = get(i);
-                if (task.mIdentifier.mDeviceId == parentIdentifier.mDeviceId &&
-                        task.mIdentifier.mObjectHandle == parentIdentifier.mObjectHandle) {
-                    remove(i);
-                    return;
-                }
-            }
-        }
     }
 
     /**
@@ -245,6 +239,7 @@
         static final int STATE_LOADING = 1;
         static final int STATE_COMPLETED = 2;
         static final int STATE_ERROR = 3;
+        static final int STATE_CANCELLED = 4;
 
         final MtpManager mManager;
         final MtpDatabase mDatabase;
@@ -272,6 +267,7 @@
 
         synchronized void loadObjectHandles() {
             assert mState == STATE_START;
+            mPosition = 0;
             int parentHandle = mIdentifier.mObjectHandle;
             // Need to pass the special value MtpManager.OBJECT_HANDLE_ROOT_CHILDREN to
             // getObjectHandles if we would like to obtain children under the root.
@@ -303,12 +299,10 @@
                 case STATE_ERROR:
                     throw mError;
             }
-
             final Cursor cursor =
                     mDatabase.queryChildDocuments(columnNames, mIdentifier.mDocumentId);
+            cursor.setExtras(extras);
             cursor.setNotificationUri(resolver, createUri());
-            cursor.respond(extras);
-
             return cursor;
         }
 
@@ -374,6 +368,10 @@
                 }
             }
             synchronized (this) {
+                // Check if the task is cancelled or not.
+                if (mState != STATE_LOADING) {
+                    return;
+                }
                 try {
                     mDatabase.getMapper().putChildDocuments(
                             mIdentifier.mDeviceId,
@@ -403,6 +401,14 @@
         }
 
         /**
+         * Cancels the task.
+         */
+        synchronized void cancel() {
+            mDatabase.getMapper().cancelAddingDocuments(mIdentifier.mDocumentId);
+            mState = STATE_CANCELLED;
+        }
+
+        /**
          * Returns a state of the task.
          */
         int getState() {
diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/Mapper.java b/packages/MtpDocumentsProvider/src/com/android/mtp/Mapper.java
index adc71ae..63f18f3 100644
--- a/packages/MtpDocumentsProvider/src/com/android/mtp/Mapper.java
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/Mapper.java
@@ -363,6 +363,41 @@
     }
 
     /**
+     * Cancels adding documents.
+     * @param parentId
+     */
+    void cancelAddingDocuments(@Nullable String parentId) {
+        final String selection;
+        final String[] args;
+        if (parentId != null) {
+            selection = COLUMN_PARENT_DOCUMENT_ID + " = ?";
+            args = strings(parentId);
+        } else {
+            selection = COLUMN_PARENT_DOCUMENT_ID + " IS NULL";
+            args = EMPTY_ARGS;
+        }
+
+        final SQLiteDatabase database = mDatabase.getSQLiteDatabase();
+        database.beginTransaction();
+        try {
+            if (!mInMappingIds.contains(parentId)) {
+                return;
+            }
+            mInMappingIds.remove(parentId);
+            final ContentValues values = new ContentValues();
+            values.put(COLUMN_ROW_STATE, ROW_STATE_VALID);
+            mDatabase.getSQLiteDatabase().update(
+                    TABLE_DOCUMENTS,
+                    values,
+                    selection + " AND " + COLUMN_ROW_STATE + " = ?",
+                    DatabaseUtils.appendSelectionArgs(args, strings(ROW_STATE_INVALIDATED)));
+            database.setTransactionSuccessful();
+        } finally {
+            database.endTransaction();
+        }
+    }
+
+    /**
      * Queries candidate for each mappingKey, and returns the first cursor that includes a
      * candidate.
      *
diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java
index 50781bf..1823711 100644
--- a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDocumentsProvider.java
@@ -308,7 +308,7 @@
             final Identifier parentIdentifier = mDatabase.getParentIdentifier(documentId);
             mMtpManager.deleteDocument(identifier.mDeviceId, identifier.mObjectHandle);
             mDatabase.deleteDocument(documentId);
-            getDocumentLoader(parentIdentifier).clearTask(parentIdentifier);
+            getDocumentLoader(parentIdentifier).cancelTask(parentIdentifier);
             notifyChildDocumentsChange(parentIdentifier.mDocumentId);
             if (parentIdentifier.mDocumentType == MtpDatabaseConstants.DOCUMENT_TYPE_STORAGE) {
                 // If the parent is storage, the object might be appeared as child of device because
@@ -402,7 +402,7 @@
             final String documentId = mDatabase.putNewDocument(
                     parentId.mDeviceId, parentDocumentId, record.operationsSupported,
                     infoWithHandle, 0l);
-            getDocumentLoader(parentId).clearTask(parentId);
+            getDocumentLoader(parentId).cancelTask(parentId);
             notifyChildDocumentsChange(parentDocumentId);
             return documentId;
         } catch (FileNotFoundException | RuntimeException error) {
diff --git a/packages/MtpDocumentsProvider/tests/src/com/android/mtp/DocumentLoaderTest.java b/packages/MtpDocumentsProvider/tests/src/com/android/mtp/DocumentLoaderTest.java
index 45f89e4..60dd7e1 100644
--- a/packages/MtpDocumentsProvider/tests/src/com/android/mtp/DocumentLoaderTest.java
+++ b/packages/MtpDocumentsProvider/tests/src/com/android/mtp/DocumentLoaderTest.java
@@ -21,6 +21,7 @@
 import android.mtp.MtpObjectInfo;
 import android.net.Uri;
 import android.provider.DocumentsContract;
+import android.provider.DocumentsContract.Document;
 import android.test.AndroidTestCase;
 import android.test.suitebuilder.annotation.MediumTest;
 
@@ -28,6 +29,7 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeoutException;
 
 @MediumTest
 public class DocumentLoaderTest extends AndroidTestCase {
@@ -141,6 +143,33 @@
         }
     }
 
+    public void testCancelTask() throws IOException, InterruptedException {
+        setUpDocument(mManager,
+                DocumentLoader.NUM_INITIAL_ENTRIES + DocumentLoader.NUM_LOADING_ENTRIES + 1);
+
+        // Block the first iteration in the background thread.
+        mManager.blockDocument(
+                0, DocumentLoader.NUM_INITIAL_ENTRIES + 1);
+        setUpLoader();
+        try (final Cursor cursor = mLoader.queryChildDocuments(
+                MtpDocumentsProvider.DEFAULT_DOCUMENT_PROJECTION, mParentIdentifier)) {
+            assertTrue(cursor.getExtras().getBoolean(DocumentsContract.EXTRA_LOADING));
+        }
+        Thread.sleep(DocumentLoader.NOTIFY_PERIOD_MS);
+
+        // Clear task while the first iteration is being blocked.
+        mManager.unblockDocument(
+                0, DocumentLoader.NUM_INITIAL_ENTRIES + 1);
+        mLoader.cancelTask(mParentIdentifier);
+
+        Thread.sleep(DocumentLoader.NOTIFY_PERIOD_MS * 2);
+
+        // Check if it's OK to query invalidated task.
+        try (final Cursor cursor = mLoader.queryChildDocuments(
+                MtpDocumentsProvider.DEFAULT_DOCUMENT_PROJECTION, mParentIdentifier)) {
+        }
+    }
+
     private void setUpLoader() {
         mLoader = new DocumentLoader(
                 new MtpDeviceRecord(